1. Field of the Invention
The present invention relates to a technical-field of a pipe bending processing apparatus and a pipe bending processing method suitable to perform small radius bending processing of a pipe.
2. Description of the Related Art
As the conventional art of this kind, the art described in JP-A-61-222634 (JP-B-2-015291) has been known. This conventional art has a structure as shown in FIG. 10.
As shown in FIG. 10, one end of a pipe P is tightened and fixed by a clamp mold 102 in a drawing and bending mold 101 for performing drawing and bending processing. The drawing and bending mold 101 rotates by a cylinder (not shown) for drawing and bending and performs the drawing and bending processing. The other end of the pipe P is tightened and fixed by a chuck 103 for performing compression bending processing. The chuck 103 moves in a pipe axis direction by a cylinder (not shown) for compression bending and performs the compression bending processing. The side the pipe P is tightened and fixed by a wiper 104 and a side bending mold 105. The side bending mold 105 moves in the pipe axis direction by a cylinder (not shown) for side bending and performs side bending processing. Incidentally, numeral 106 is a mandrel and is fixed in the top of a mandrel shaft 107.
In the structure, the drawing and bending mold 101 and the chuck 103 are actuated to perform the drawing and bending processing and the compression bending processing and simultaneously the side bending mold 105 is actuated to perform the side bending processing and thereby, bending processing of a small radius of the pipe can be performed while suppressing a reduction in wall thickness occurring in the back side of a bending processing part.
However, in the conventional art described above, the wiper 104 is located in a pipe compression direction of the chuck 103 for pressing the other end of the pipe P, so that the chuck 103 can pressurize the pipe only until just before interfering with the wiper 104. Therefore, as shown in FIG. 11, an extrusion margin 10 must be left for the other end of the pipe P, so that there were problems that a step of cutting an unnecessary portion of this extrusion margin 10 after processing is required and also yield is low since the cut portion becomes waste.